What are the common anti-rust treatment processes for Q235NH steel plates?

1. Enhancing the Native Weathering Oxide Film (Ideal for Long-Term Outdoor Use)

Leveraging Q235NH's alloying elements (Cu, P, Cr, etc.), this process accelerates or strengthens the formation of its dense surface oxide film-the core of its rust resistance-without relying on external coatings.

: Expose the steel to outdoor environments with alternating wet and dry conditions (e.g., periodic misting with clean water) to promote the growth of a stable, adherent oxide layer (typically taking 3–6 months). This film self-repairs minor scratches over time.

: Apply a specialized weathering steel passivation solution (containing phosphates or organic inhibitors) to the surface. After 10–15 minutes of reaction, rinse and dry. This accelerates the formation of a dense oxide film, reducing natural weathering time by 50% or more.

2. Surface Coating Protection (For Harsh Environments or Aesthetic Needs)

When the native oxide film alone is insufficient (e.g., high humidity, salt spray, or decorative requirements), coatings provide extra protection:

Weather-resistant paint systems: Use polyurethane or fluorocarbon topcoats (with inorganic zinc-rich primers for better adhesion). These coatings resist UV radiation and moisture, extending service life to 8–10 years outdoors. Ideal for structural parts in coastal or industrial areas.

: For decorative applications (e.g., architectural panels), apply a transparent fluorocarbon clear coat after the oxide film forms. This preserves the steel's natural "rusty patina" while blocking further corrosion.

3. Temporary Rust Prevention (For Storage or Transportation)

To prevent rust during storage, transportation, or pre-installation:

Rust-preventive oil/wax: Apply a thin layer of neutral mineral oil-based rust-preventive oil or wax to isolate the surface from moisture and air. Easily removable with solvents before final use.

: Wrap the steel in VCI film or paper. VCI molecules volatilize to form a protective layer on the metal surface, suitable for sealed storage (effective for 1–2 years).

These processes are selected based on factors like service environment, lifespan requirements, and cost. For long-term outdoor use, enhancing the native oxide film (with or without topcoats) is most cost-effective, while temporary methods suit short-term protection needs.

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